Two-dimensional kinetic analysis of a Hall thruster discharge with a null-magnetic point at the anode

A two-dimensional axial-radial particle-in-cell model is used to analyze the electron response in a non-shielded 5 kW class Hall thruster. Radial asymmetries in the plasma discharge are present due to the cylindrical thruster geometry and the magnetic topology. The applied magnetic field presents a near-null point at the anode, from which a magnetic separatrix (MS) is born. Downstream of the MS, the plasma response is standard for a magnetic lens topology and agrees well with previous studies. In contrast, upstream of the MS, the magnetic field is nearly axial and partially shields the lateral walls. The magnetized electrons cannot easily cross the MS and are channeled toward the near-null magnetic point at the anode. This leads to sharp changes in the bulk plasma properties, significantly decreasing particle and energy fluxes to the walls. The lack of electrons reaching the outer dielectric wall upstream of the MS leads to the collapse of the classical electron-repelling sheath structure in order to comply with the dielectric condition. Electrons in this region are heated, and their inertia becomes comparable to their thermal energy. Moreover, consistently with previous simulations assuming a radial magnetic field, the electron response differs from a collisional fluid in terms of wall interaction properties, heat flux, and finite Larmor radius effects.

Two-dimensional kinetic analysis of a Hall thruster discharge with a null-magnetic point at the anode Articles